SUNOL — It could take several days for the Altamont Commuter Express to get rolling again as crews clean up the damage caused when ACE train No. 10 was derailed by a mudslide Monday night.

Union Pacific spokesman Francisco Castillo said Tuesday morning that the goal is to have the ACE train — locomotive, three cars that stayed on the rails, and one that derailed but stayed upright — out of the canyon by the end of the day.

Getting the fifth car, the one that remained in Alameda Creek on Tuesday morning, out will be more difficult; Castillo said large cranes owned by UP and others owned by an independent contractor will be needed to lift the car out of the water and onto a flatbed. Whether that flatbed will be a rail car or a flatbed truck trailer, necessitating a move out of the canyon on Highway 84, was undetermined as of Tuesday morning, Castillo said.

He said that a mudslide indeed appears to have caused the derailment, but it wasn”t known whether the mud flowed onto the tracks before ACE train No. 10 got to that spot in the canyon, or whether it struck the lead rail car broadside as the train rolled past.

“That”s part of the investigation,” Castillo said.

ACE trains operate in “push-pull” mode; its trains headed from San Jose to Stockton are in “push” mode, with the locomotive pushing the cars. The engineer was in the car that ended up in the creek. Most of the United States” urban commuter rail operations — including CalTrain on the peninsula — operate this way, as do Amtrak”s Capitol Corridor and San Joaquin trains, and some high-speed Amtrak trains in the Midwest.

Tuesday morning, it appeared that it would take at least a few days to get the track through Niles Canyon back in service, Castillo said.

The UP line through Niles Canyon is lightly used by freight trains — typically, only three in each direction per day. Castillo was not sure whether those trains are being rerouted, or simply canceled, while the Niles Canyon track is out of service.

ACE has a contract with UP that allows the commuter carrier to operate four trains in the morning and four trains in the evening, said Steve Walker, ACE”s safety and security coordinator.

Castillo said he didn”t know whether the stretch of UP track through Niles Canyon has suffered notable mudslides over the years. All UP tracks in California are subject to a “very robust” inspection process, and the tracks had gone through an additional “stormwatch” inspection just ahead of this weekend”s rainstorms, he said.

“It”s impossible to know when mudslides are going to happen,” he said.

Christopher Chow, a spokesman for the California Public Utilities Commission, said the agency sent two inspectors to the scene Monday night, and they remain on site.

“Their focus is on identifying the root cause of the incident and collecting evidence to determine if there were any violations by ACE,” Chow said. “As part of the investigation, we will be reviewing relevant records, including our last inspection of the track.”

SUNOL — It could take several days for the Altamont Commuter Express to get rolling again as crews clean up the damage caused when ACE train No. 10 was derailed by a mudslide Monday night.

Union Pacific spokesman Francisco Castillo said Tuesday morning that the goal is to have the ACE train — locomotive, three cars that stayed on the rails, and one that derailed but stayed upright — out of the canyon by the end of the day.

Getting the fifth car, the one that remained in Alameda Creek on Tuesday morning, out will be more difficult; Castillo said large cranes owned by UP and others owned by an independent contractor will be needed to lift the car out of the water and onto a flatbed. Whether that flatbed will be a rail car or a flatbed truck trailer, necessitating a move out of the canyon on Highway 84, was undetermined as of Tuesday morning, Castillo said.

He said that a mudslide indeed appears to have caused the derailment, but it wasn”t known whether the mud flowed onto the tracks before ACE train No. 10 got to that spot in the canyon, or whether it struck the lead rail car broadside as the train rolled past.

“That”s part of the investigation,” Castillo said.

ACE trains operate in “push-pull” mode; its trains headed from San Jose to Stockton are in “push” mode, with the locomotive pushing the cars. The engineer was in the car that ended up in the creek. Most of the United States” urban commuter rail operations — including CalTrain on the peninsula — operate this way, as do Amtrak”s Capitol Corridor and San Joaquin trains, and some high-speed Amtrak trains in the Midwest.

Tuesday morning, it appeared that it would take at least a few days to get the track through Niles Canyon back in service, Castillo said.

The UP line through Niles Canyon is lightly used by freight trains — typically, only three in each direction per day. Castillo was not sure whether those trains are being rerouted, or simply canceled, while the Niles Canyon track is out of service.

ACE has a contract with UP that allows the commuter carrier to operate four trains in the morning and four trains in the evening, said Steve Walker, ACE”s safety and security coordinator.

Castillo said he didn”t know whether the stretch of UP track through Niles Canyon has suffered notable mudslides over the years. All UP tracks in California are subject to a “very robust” inspection process, and the tracks had gone through an additional “stormwatch” inspection just ahead of this weekend”s rainstorms, he said.

“It”s impossible to know when mudslides are going to happen,” he said.

Christopher Chow, a spokesman for the California Public Utilities Commission, said the agency sent two inspectors to the scene Monday night, and they remain on site.

“Their focus is on identifying the root cause of the incident and collecting evidence to determine if there were any violations by ACE,” Chow said. “As part of the investigation, we will be reviewing relevant records, including our last inspection of the track.”